1. Field of the Invention
This invention relates to a focus detection device for use in a Camera or the like which uses a light beam transmitted through an imaging optical system to detect the imaged state thereof.
2. Related Background Art
In a focus detection device of the phase difference detection type, a method of correcting the distortion of the distribution of the quantity of light projected onto a photoelectric conversion element by calculating the output of the photoelectric conversion element is disclosed, for example, in Japanese Patent Application Laid-Open No. 62-173412. This example discloses a calculating method which relates distortion occurring to a secondary object image to a corrected image, and processes an image signal after A/D-converted by a predetermined calculating method shown in this publication, and returns the distortion to its original state, whereby it can accurately effect the determination of the in-focus of an objective lens.
However, depending on an optical system adopted in the focus detection device, there is a case where the movement speed of the image resulting from the defocus of the objective lens differs depending on the position on a focus detection area and as the result, the detection of the defocus amount is not accurately effected. Accordingly, accurate focus detection cannot be accomplished simply by correcting distortion by the method as described above.